In general, most printers include an automatic paper feeding device for automatically feeding paper, where the automatic paper feeding device includes a separator, which is in contact with the front of the paper, to separate and feed the paper one by one.
In the automatic paper feeding device, when a control signal is received to convey the paper to print, the paper feeding roller operates to convey the paper. When the paper is conveyed, the front end of the paper is separated by the separator, so that the paper is supplied one sheet at a time. Such a separator easily separates ordinary printer paper, supplying it one sheet at a time. However, thick paper such as envelopes and post cards, cannot be conveyed through the separator because the front end of the thick paper jams and cannot be conveyed any more.
There needs to be different conveyance paths for standard and thick paper, which require a mechanism to separate the feed of standard paper from the feed of thick paper. As shown in FIGS. 1 and 2, when thick paper is conveyed through a printer 100's "L"-shaped lever 101, which is installed at the side of the paper feeding device, the "L"-shaped lever is turned so that the thick paper can be conveyed with one face being in contact with the "L"-shaped lever. Accordingly, it is conveyed in a way that bypasses the separator.
Unfortunately, this paper switching device has an ugly appearance and is difficult to use. What is needed is a paper guide that allows thick documents such as envelopes and postcards to bypass the paper separator. U.S. Pat. No. 4,457,507 for a Sheet Feeding Apparatus to Ishikawa et al. discloses a sheet feeding apparatus that contains a fixed guide and an adjustable guide. In addition, a roller is shown for separating sheets of paper fed into the printer.
U.S. Pat. No. 4,828,245 for a Sheet Feeder Suitable For Feeding Thick Sheets to Shimogawara discloses a thick sheet feeding attachment having a pair of slits separated by a distance smaller than the distance between pawls used for separating thin sheets, thereby disabling the separating function of the pawls.
U.S. Pat. No. 5,348,283 for a Sheet Feeding Apparatus Having Sheet Separating Means With Adjustable Feeding Force to Yanagi et al. discloses a sheet feed apparatus can accommodate both thin sheets as well as thick sheets like postcards and envelopes.
I have not seen a sheet feeding apparatus made up of a guide positioned on a knock-up plate and orientated to guide paper in a direction perpendicular to the paper's movement so as to bypass the sheet separator.